Starter-pawl ratchet clutch snubber

ABSTRACT

A snubber disposed in proximity to and in cooperation with the ratchet of a pawl/ratchet clutch of a pneumatically driven starter serves to prevent breakage of the component parts of the starter in the event that less than the total number of pawls engage the ratchet when in the driving condition.

United States Patent 1 1 1111 3,727,733

Mrazek 51 Apr. 17, 1973 STARTER-PAWL RATCHET CLUTCH [56] References Cited SNUBBER UNITED STATES PATENTS [75] Inventor: James A. Mrazek, South Glastonbuy Conn 1,114,304 10/1914 Stanley ..192/46 X 2,625,047 1/1953 Wood ..74/7 C [73] Assignee: United Aircraft Corporation, East 2,721,482 10/1955 Shank et a1. ..60/39.14 X H tf d Conn 2,728,234 12/1955 Volk, Jr. et a1. ..74/7 c [22] Filed: May 1972 Primary Examiner--A11an D. Herrmann 1 APPL 251 4 3 ArrorneyNorman Friedland [57] ABSTRACT [52] US. Cl. ..l92/42, 74/7 C, 74/7 E,

192 4 92 104 C A snubber disposed in proximity to and in cooperation 51 Int. Cl. ..Fl6d 41/12, F02n 15/02 with the ratchet of a pawl/ratchet clutch of pneu- [58] Field of Search ..192/42, 46, 63, 104 c; matically driven Starter Serves to Prevent breakage of 0/3914; 74 7 E, 7 C the component parts of the starter in the event that less than the total number of pawls engage the ratchet when in the driving condition.

7 Claims, 2 Drawing Figures PATENTEDAFRWQB 3.727. 733

' SHEET 1 [if Q STARTER-PAWL RATCHET CLUTCH SNUBBER BACKGROUND OF THE INVENTION This invention relates to pneumatic starters particularly suited for start-ups of jet powered aircraft and is directed to means for preventing breakage in the event that one or more but less than the total number of pawls in the clutch engage the ratchet.

This invention solves the problem of breakage of component parts of the starter occasioned when one or less than the total number of pawls in a pawl/ratchet clutch engage the ratchet with resulting side loads. To appreciate the problem, it has been found that when a single pawl engagement occurs as during a running engagement or crash engagement, radial or side forces in the order of 14,000 pounds have been known to develop and transmitted through the inlet housing and transmission housing with sufficient force resulting in breakage of the inlet housing strut.

To obviate the problem noted above I provide a snubber affixed to a bore formed in the driven output shaft located in proximity to the rotating ratchet but spaced therefrom a sufficient distance such that when a side load of significant magnitude occurs as a result of the pawl operating improperly the ratchet engages the snubber prior to the point of starter component breakage so as to shunt the load and avoid fracturing.

SUMMARY OF THE INVENTION A primary object of this invention is to provide means for preventing breakage of component parts of a starter occasioned when less than the totalnumber of pawls in a pawl/ratchet clutch engage the ratchet.

A still further object of this invention is to provide an improved turbine type of power plant starter including I a snubber located in proximity to the ratchet of a pawl/ratchet clutch and spaced therefrom and rendered inoperative during normal operation but cooperative therewith to absorb the radial load occasioned by a malfunction of the pawl so as to shunt the attendant side loading.

Other features and advantages will be apparent from the specification and claims and from the accompanying drawing which illustrates an embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partial view in cross section illustrating the details of this invention, and

FIG. 2 is a sectional view taken along lines 22 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT A typical starter where this invention is particularly efficacious is exemplified by starter P8600 manufactured by the Hamilton Standard Division of United Aircraft Corporation for the L-lll Lockheed Aircraft. While this invention is described in its preferred embodiment as being efficacious in a starter application, it is to be understood as will be appreciated by one skilled in this art that this invention would have similar appli cations to other pawl/ratchet clutches and particularly to those operating at significantly high speeds where side loadings would be occasioned by the improper engagement of the pawls.

'are eliminated therefrom for the sake of clarity-and simplicity. The turbine of pneumatic starters driven by pressurized air serve to extract pneumatic energy and convert it to mechanical energy. Typically, an air valve- (not shown) is utilized which communicates with the pressurized source of air and upon initiation of starting is opened to admit air to the turbine so as to drive the engine through the spline output shaft and pawl/ratchet clutch. The starter for the L-lOll aircraft, supra, for example, is designed to accelerate the engine from zero to idle speeds (approximately 6450 rpm) in approximately 45.5 seconds at sea level, standard day conditions. Once light off has occurred and the engine reaches a predetermined speed, an electrical signal closes the valve and shuts off the air supply so that when the engine speed'overrides the starter speed, the clutch pawl is released and rides free above the ratchet teeth on the output end of the starter and the turbine coasts to a stop. The power extracted from the turbine either through a gear reduction or directly serves to drive gear 18 supported on shaft 20 journaled in bearings 22 formed in housing strut 24. Pinion gear 26 formed integral with the gear 18 drives the ring gear 30 which rotatably supported by bearings 32 also supported to housing strut 24. Ratchet 36 carried by the ring gear support 38 carries a plurality of rake teeth 40 which cooperate with a plurality of pawls 42, circumferentially and equally spaced about the rotating center line to evenly distribute the load.

As is shown in FIG. 2 three pawls are employed although not specifically limited thereto, and each of the pawls 42 are rotatably supported on shaft 44 carried by radial extension portion 46 of the output splined shaft 48 which is rotatably supported by bearings 50 to the housing 14. A plurality of leaf springs 52 secured to the inner diameter of the extension portion 46 by a nut and bolt arrangement 54 spring loads the pawls in engagement to the ratchet and assures that the pawls are engaged to the ratchet at speeds say below 3,800 rpm.

In accordance with this invention a generally cylindrically shaped snubber 60 having a smaller diameter portion 62 is shrunk fitted into bore 64 formed centrally in the inner end of output splined shaft 48 and rotates therewith. A larger diameter portion 66 extends radially outward relative to the center line and terminates in proximity to but spaced from the inner diameter of ratchet 36. Ring gear support 38 is dimensioned relative to bearings 32 to permit slight cocking movement so that in the event that less than the three pawls 42 engage theratchet, the attendant side loads will permit the ratchet and ring gear support to, rock about bearing 32 and allow ratchet 36 to engage snubber 66. This serves to shunt the side loads through the snubber 66, through the radial extension portion 46, through the shaft 44 and back through the pawl 42.

Without the snubber, this side load heretofore was transmitted through the ratchet 36, through the bearing 32, through the housing 25, through the housing 14, through the bearing 50, through the extension portion 46, through the shaft 44, and back through the pawl 42 usually resulting in fracturing of the strut 24 which is formed as a part of the inlet housing 12.

It should be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the spirit or scope of this novel concept as defined by the following claims.

I claim:

1. A rotary clutch having a rotary drive including a ratchet, a driven member, a plurality of pawls disposed circumferentially about said ratchet and operable therewith to transmit rotary motion from said ratchet member to said driven member, a snubber secured to said driven member and rotating therewith and having an extension portion in close proximity to said ratchet and normally out of engagement therewith, said ratchet engaging said extension portion of said snubber when less than the total number of said pawls engage said ratchet so as to shunt the side loads produced thereby to said pawls and said ratchet.

2. A rotary clutch as claimed in claim 1 wherein said extension portion of said snubber is disposed adjacent the inner diameter of said ratchet.

3. A rotary clutch as claimed in claim 1 wherein said snubber is press fitted into a central bore formed centrally on one end of said driven member.

4. A rotary clutch as claimed in claim 1, including a gear gage rotatably supported by a rotary bearing means, said ratchet being a ring-like element integrally connected to said gear gage, said bearing means having sufficient looseness to permit said ring-like element to be displaced about an axis transverse to the rotating center line to permit engagement thereof with said extension portion prior to fracturing of said gear gage.

5. A rotary jet engine starter having a driven output shaft, means including a gear for imparting rotary motion to said driven shaft, a ratchet-pawl clutch interconnecting said gear and said driven output shaft, said ratchet being a ring-like element, a snubber secured to said shaft and driven thereby normally out of engagement with said ratchet and in engagement with said ratchet when less than the total number of pawls engage said ratchet so as to transmit the side loads produced by said engaged pawl thru said ratchet, said snubber and back to said pawl.

6. A rotary jet engine starter as claimed in claim 5 wherein said snubber is attached to said output shaft and driven thereby and said snubber includes a cylindrical extension portion mounted juxtaposed to but spaced from the inner diameter of said ring-like element so as to be normally out of engagement and in engagement when less than the number of pawls engage said ratchet.

7. A rotary clutch having a rotary drive including a ratchet, a driven member, a plurality of pawls disposed circumferentially about said ratchet and operable therewith to transmit rotary motionfrom said ratchet member to said driven member, a snubber operatively connected to said driven member and rotating therewith and having an extension portion in close proximity to said ratchet and normally out of engagement therewith, said ratchet engaging said extension portion of said snubber when less than the total number of said pawls engage said ratchet so as to shunt the side loads produced thereby to said pawls and said ratchet. 

1. A rotary clutch having a rotary drive including a ratchet, a driven member, a plurality of pawls disposed circumferentially about said ratchet and operable therewith to transmit rotary motion from said ratchet member to said driven member, a snubber secured to said driven member and rotating therewith and having an extension portion in close proximity to said ratchet and normally out of engagement therewith, said ratchet engaging said extension portion of said snubber when less than the total number of said pawls engage said ratchet so as to shunt the side loads produced thereby to said pawls and said ratchet.
 2. A rotary clutch as claimed in claim 1 wherein said extension portion of said snubber is disposed adjacent the inner diameter of said ratchet.
 3. A rotary clutch as claimed in claim 1 wherein said snubber is press fitted into a central bore formed centrally on one end of said driven member.
 4. A rotary clutch as claimed in claim 1, including a gear gage rotatably supported by a rotary bearing means, said ratchet being a ring-like element integrally connected to said gear gage, said bearing means having sufficient looseness to permit said ring-like element to be displaced about an axis transverse to the rotating center line to permit engagement thereof with said extension portion prior to fracturing of said gear gage.
 5. A rotary jet engine starter having a driven output shaft, means including a gear for imparting rotary motion to said driven shaft, a ratchet-pawl clutch interconnecting said gear and said driven output shaft, said ratchet being a ring-like element, a snubber secured to said shaft and driven thereby normally out of engagement with said ratchet and in engagement with said ratchet when less than the total number of pawls engage said ratchet so as to transmit the side loads produced by said engaged pawl thru said ratchet, said snubber and back to said pawl.
 6. A rotary jet engine starter as claimed in claim 5 wherein said snubber is attached to said output shaft and driven thereby and said snubber includes a cylindrical extension portion mounted juxtaposed to but spaced from the inner diameter of said ring-like element so as to be normally out of engagement and in engagement when less than the total number of pawls engage said ratchet.
 7. A rotary clutch having a rotary drive including a ratchet, a driven member, a plurality of pawls disposed circumferentially about said ratchet and operable therewith to transmit rotary motion from said ratchet member to said driven member, a snubber operatively connected to said driven member and rotating therewith and having an extension portion in close proximity to said ratchet and normally out of engagement therewith, said ratchet engaging said extension portion of said snubber when less than the total number of said pawls engage said ratchet so as to shunt the side loads produced thereby to said pawls and said ratchet. 